Mobile radio communication services have become extremely popular over the last couple of decades. However, mobile radio resources are scarce, and there is a great need of using the available resources in an efficient manner.
One way of increasing the efficiency of the utilisation of the radio resources is to reduce the amount of control information that is signalled between the radio base station and the mobile stations. When the radio resources used for the transmission of control information is decreased, the amount of radio resources that is available for the transmission of payload is increased.
In the 3GPP Technical Specification 25.213, section 4.6.2.3, a method of allocating a number of spreading codes to a mobile station is disclosed. According to the specification, 15 different spreading codes are available for allocation to one or more mobile stations, each spreading code being identified by a consecutive number. The allocation of spreading codes to a mobile station is signalled to the mobile station by signalling the number identifying the first of the spreading codes that have been allocated to the mobile station, and the number of spreading codes that have been allocated. Hence, if the number of spreading codes allocated to the mobile station exceeds two, the amount of radio resources needed to signal the allocation will be lower than if a spreading code identification would have to be transmitted for each spreading code.